In recent years, in order to cope with miniaturization and enhancement of performance of various electronic devices, the size of electronic components to be mounted has been increasingly reduced. Accordingly, as the method of mounting electronic components onto a circuit substrate, solder reflow, which is a process capable of obtaining a high mounting density and high manufacturing efficiency, has been commonly used. Furthermore, in recent years, since use of Pb-free solder having high melting point has been desired in view of environmental problems, in the solder reflow process, heating has been performed at a high temperature of 220° C. to 270° C. Consequently, the electronic components have also been desired to have heat resistance that can withstand such a high temperature.
Examples of the electronic components include components into which members requiring transparency, such as optical lenses and transparent films, are built. In the past, as such members requiring transparency, moldings of inorganic glass and transparent thermoplastic resins have been used (Non-Patent Document 1).
Non-Patent Document 1: Kokomadekita tomei-jushi (Transparent resin update), Kogyo Chosakai Publishing, Inc., 2001, p. 48